Patent GB-851076-A (GB)
Title: Improvements in or relating to methods of forming electroluminescent coatings
IPC: H05B33/10
Filed: 1956-12-31
Abstract: In a method of forming an electroluminescent coating of at least one activating oxide and one activated oxide on an electrode of an electron-optical converter, an alloy of the metals and/or metalloids of the oxides is formed on an intermediate base plate, material is transferred from the base plate to the electrode, an oxygen atmosphere is introduced into the space between the base plate and the electrode either before the transfer commences or after the completion of the transfer, the material formed on the electrode is oxidized by the oxygen atmosphere before or after the completion of the transfer, and the oxide coating so produced is crystallized. Oxygen molecules can be introduced into the oxide coating.  The oxides can be as described in Specification 850,592 and can be of zinc, calcium, barium and cadmium for the activated oxides, and of copper, lead manganese, silver, thallium, selenium and germanium for the activating oxides.  In an example a base plate of magnesium or aluminium is placed in a vessel and crucibles containing pure or impure metals and/or metalloids are isotropically arranged with respect to the base plate.  The vessel is evacuated to 10-4 mm. and the crucibles heated to effect thermal evaporation and form alloys on the cooled base plate, and the vessel is then cooled.  The areas of the surface of evaporation of the different metals and/or metalloids are proportioned with respect to the temperature of evaporation so as to determine the respective amounts of the various components in the alloy.  An optically polished nickel or rhodium electrode is placed in the vessel into which pure oxygen at 10-1 mm. is introduced.  A D.C. potential is applied between the base plate and the electrode, particles from the base plate being oxidized as soon as they are extracted from the alloy, or even sooner, due to the oxygen atmosphere.  The oxide coating on the electrode is then submitted to H.F. thermal treatment to effect crystallization. Alternatively the heat treatment can be effected during the transfer and oxidizing operation to form a single crystal of a complex of oxides.  The electrode is then cooled and a translucent film of silver or aluminium is formed over the oxide layer by evaporation under reduced pressure.  In the above process uncombined molecules of oxygen are formed in the oxide layer by diffusion, the amount being governed by the pressure of the oxygen and by the temperature of crystallization. In a modified process transfer of an alloy of the metals and/or metalloids from the base plate to the electrode is effected in an inert gas such as argon and the oxidizing and crystallizing steps are effected after the transfer is completed.  In a further modification an oxygen atmosphere is introduced into the vessel before the transfer operation and such a D.C. potential is applied between the base plate and the electrode as to oxidize the surface of the alloy on the base plate.  Then an inert gas such as argon is substituted for the oxygen for the transfer of the oxides to the electrode. Crystallization can be effected either during such transfer whereafter the crystal is heated in oxygen for the diffusion therein of uncombined molecules of oxygen, or later and if done by heating in oxygen the introduction of uncombined molecules of oxygen is simultaneously effected.